N-{8 (Substituted amino) thio{9 -imides

ABSTRACT

Imides such as N-(morpholinothio)phthalimide are used to affect the vulcanization characteristics of sulfur vulcanizable polymers by increasing the state of vulcanization and/or improving scorch resistance and/or increasing the rate of vulcanization.

United States Patent [191 Lawrence N-[(SUBSTITUTED AMINO) THIO]-IMIDES[75] Inventor: John P. Lawrence, Stow, Ohio [73] Assignee: The GoodyearTire & Rubber Company, Akron, Ohio [22] Filed: .Mar.7, 1974 21App1.No.:448,856

Related US. Application Data [62] Division of Ser. No. 266,008, June 26, 1972, Pat. No.

[58] Field of Search... 260/247.1 L, 326.5 S, 268 S, 260/293.71, 293.61,293.69, 326 S [56] References Cited UNITED STATES PATENTS Lambrech eta1. 260/268 S Dec. 23, 1975 3,071,592 1/1963 Ladd 260/326.5 S 3,178,4474/1965 260/326.5 S 3,410,842 11/1968 Allais et al 260/326.5 S 3,525,7378/1970 Kern et a1 260/326.5 S 3,546,185 12/1970 Coran et a1 260/326.5 S

FOREIGN PATENTS OR APPLICATIONS 1,355,802 6/1974 United Kingdom PrimaryExaminer-Anton l-l. Sutto Assistant Exam'iner-Michael Shippen Attorney,Agent, or Firm-F. W. Brunner; J. A. Rozmajze ABSTRACT ,lmides such asN-(morpholinothio)phthalimide are used to affect the vulcanizationcharacteristics of sulfur vulcanizable polymers by increasing the stateof vulcanization and/or improving scorch resistance and- /or increasingthe rate of vulcanization.

2 Claims, No Drawings N-[ (SUBSTITUTED AMINO) THIOl-IMIDES This is adivisional application of application Ser. No. 266,008 filed June 26,1972, which issued on Sept. 24, 1974 as US. Pat. No. 3,838,114.

This invention relates to compounds which generally function to increasethe state (degree) of vulcanization when used during the sulfurvulcanization of rubbers by donating sulfur tto the system. Thisinvention also relates to compounds which provide a vulcanizable polymerwith balanced processing and vulcanization characteristics. In addition,it relates to compounds which retard vulcanization during the processingof vulcanizable rubbery compositions. It also relates to compounds whichfunction as activators, that is, secondary accelerators in sulfur typevulcanization systems. It also relates to processes for increasing thestate of vulcanization of sulfur vulcanizable rubbery compositions andeither increasing scorch delay periods and/or increasing vulcanizationrates. It also relates to the vulcanized products resulting therefrom.

The physical properties of a vulcanized composition are related to itsstatevof vulcanization. Often, as the state of vulcanization isincreased, certain physical properties are improved. Rubber additivessuch as sul fur donors can be used therefore to increase the state ofvulcanization or to permit the use of lesser amounts of free sulfur.

Scorching duringtthe processing of rubber is due to the premature orinsipient vulcanization which can occur during any of the steps involvedin the processing of the rubber prior to the final vulcanization step orduring storage between said processing steps. Whereas a properlycompounded unscorched rubber formulation can be die extruded or sheetedsmoothly from a calender without lumping, a scorched material oftenbecomes wavy or lumpy after sheeting and must be discarded. It istherefore desirable that rubber additives be used which reducescorching. Such compounds are commonly referred to as retarders.

It is often desirable to increase the rate at which rubbery compositionsare vulcanized. Sulfur vulcanizable rubbery compositions containing freesulfur are made to vulcanize more rapidly by the addition of anaccelerator compound. Often the accelerator compound is referred to as aprimary accelerator and is used in combination with another acceleratorcalled an activator or secondary accelerator which further increases thevulcanization rate.

It is an object of this invention to provide sulfur donors which willincrease the state of vulcanization of vulcanized rubbery polymers aswell as compounds which are secondary accelerators (activators) and/orretarders (scorch inhibitors). Another object of the present inventionis to provide processes which will improve the scorch resistance andrate of vulcanization of vulcanizable rubbery polymers and also thestate of vulcanization of sulfur vulcanized rubbers.

The objects of the present invention are accom plished by a sulfurvulcanizable combination of a sulfur vulcanizable rubber and at leastone compound having the following structural formulae E and wherein A isan N,N-disubstituted radical selected from the group consisting of a. anN,N-disubstituted radical which is a derivative of a heterocyclicdiamine,

wherein R is asaturated or olefinic divalent aliphatic radical having 1to 7 carbon atoms, such as an alkylene radical or alkenylene radical ora saturated or olefinic divalent cyclic aliphatic radical having 5 to 10carbon atoms such as a cycloalkylene, cycloalkenylene, or aryleneradical having 6 to 10 carbon atoms and wherein R and R are selectedfrom the group consisting of alkyl radicals having 1 to 20-carbon atoms,cyano alkyl radicals having 2 to 21 carbon atoms, cycloalkyl radicalshaving 5 to 20 carbon atoms, aralkyl radicals having 7 to 20 carbonatoms and aryl radicals (e.g., phenyl, p-tolyl, alkoxyaryl, haloaryl andnitroaryl)having 6 to 20 carbon atoms, wherein R and R can be joinedthrough a member of the group consisting of CH O, and S- to constitutewith the attached nitrogen atom a heterocyclic ring, and wherein X isselected from the group consisting of alkylene radicals having 2 to 10carbon atoms, cycloalkylene radicals having 5 to 10 carbon atoms andarylene radicals having 6 to 10 carbon atoms.

Preferably R is 4,5-cyclohexenylene, orthophenylene, ethylene,or-l,3-propylene. Preferably is morpholino, 2,6-dimethylmorpholino,piperidino, diethylamino, diisopropylamino, 3-methylpiperidino,t-butylamino, dicyclohexylamino, N-B-cyanoethylcyclohexylamino,NB-cyanoethyl-t-butylamino, N-B- cyanoethyl-n-butylamino,N-phenylcyclohexylamino, N-methylanilino, N-ethylanilino,N-ethylbenzylamino, dibenzylamino, N-phenylbenzylamino,N-cyanomethylcyclohexylamino, and N-cyanomethyl-nbutylamino.

Preferably when'A is an N,N'-disubstituted radical which is a derivativeof a heterocyclic diamine, the diamine is piperazine, imidazolidine,hexahydropyrimi- 3 dine, or homopiperazine, said amines (radicals) beingunsubstituted or substituted on the ring carbons by methyl groups, thetotal number of methyl groups being less than three. It should beunderstood that the above radicals need not actually be derived from theabove diamines but need only be the radicals which can be derived fromsaid diamines. That is, the compounds are not limited to their method ofpreparation.

More preferably A is piperazine, 2,5-dimethylpiperazine, imidazolidine,hexahydropyrimidine, homopiperazine, N,N'-dimethylethylenediamine,N,N'-dimethyll,3-propylenediamine, N,N-dimethyl-l,6-hexamethylenediamine, N,N'-dimethyl-l,4-cyclohexylenediamine,N,N'-dimethyl-p-phenylenediamine, 4,4- ethylenedi(piperidine),4,4-trimethylenedi(piperidine), 4,4-tetramethylenedi(piperidine) or4,4'-hexamethylenedi(piperidine).

Compounds which act both as retarders and activators in SBR includecompounds where R is orthophenylene or 1,2-cyclohex-4-enylene and ismorpholino, N-phenylcyclohexylamino, N-B-cyanoethylcyclohexylamino,N-/3-cyanoethyl-n-butylamino, N-ethylbenzylamino orN-cyanomethylcyclohexylamino. Where R is one of the two radicalsdescribed above and is N-phenylbenzylamino the compounds are retarders.The following compounds illustrate, but do not limit, the imides of thepresent invention. N-(morpholinothio)-phthalimideN-(2,6-dimethylmorpholinothio)-phthalimideN-(piperidinothio)-phthalimide N-( 3 -methylpiperidinothio )-phthalimideN(4-methylpiperidinothio)-phthalimide N-(pyrrolidinothio)-phthalimideN-(diethylaminothio)-phthalimide N-(di-n-propylaminothio)-phthalimideN-(diisopropylaminothio)-phthalimide N-(di-n-butylaminothio)-phthalimideN-(diisobutylaminothio)-phthalimide N-(di-n-hexylaminothio)-phthalimideN-(di-n-octylaminothio)-phthalimideN-(dicyclohexylaminothio)-phthalimideN-(N'-methylcyclohexylaminothio)-phthalimideN-(dibenzylaminothio)-phthalimideN-(morpholinothio)-cisA-tetrahydrophthalimideN-(morpholinothio)-succinimide N-(piperidinothio)-succinimideN-(morpholinothio)-maleimide N-(dibenzylaminothio)-maleimideN-(morpholinothio)-glutarimideN-(2,6-dimethylmorpholinothio)-glutarimide N-(morpholinothio)-l,8-naphthalimide N-(N'-methylcyclohexylaminothio)-l ,S-naphthalimideN-(morpholinothio)-hexahydrophthalimideN-(di-n-propylaminothio)-hexahydrophthalimideN-(morpholinothio)-adipimide N-(4-methylpiperidinothio)-adipimideN-(morpholinothio)-5,S-dimethylglutarimide 4N-(3-methylpiperidinothio)-5,S-dimethylglutarimideN-(morpholinothio)-[2.2.l ]-bicyclohept-4-ene-2,3- dicarboximideN-(morpholinothio)-malonimideN-(N'-phenylcyclohexylaminothio)-phthalimideN-(N'-B-cyanoethylcyclohexylaminothio) phthalimideN-(N-B-cyanoethyl-n-butylaminothio)-phthalimideN-(N'-ethylbenzylaminothio)-phthalimideN-(N-phenylbenzylaminothio)-phthalimideN-(N-cyanomethylcyclohexylaminothio)-phthalimideN,N'-dimethyl-N,N'-bis(phthalimidothio)-ethylenediamineN,N-dimethyl-N,N'-bis(phthalimidothio )-l ,3- propylenediamine N,N'-dimethyl-N,N-bis(phthalimidothio)-l ,6-hexamethylenediamine N,N-dimethyl-N,N-bis(phthalimidothio)-l ,4- cyclohexanediamineN,N-dimethyl-N,N-bis(phthalimidothio)-pphenylenediaminel,4-Bis(phthalimidothio )-piperazine l,4-Bis(phthalimidothio)-homopiperazine l,4-Bis(phthalimidothio )-2,5-dimethylpiperazine l,3-Bis( phthalimidothio )-imidazolidine l ,3-Bis(phthalimidothio)-hexahydropyrimidine 4,4'-Ethylenedi(piperidinothio)-bis-(phthalimide)4,4-Tetramethylenedi(piperidinothio)-bis(phthalimide)4,4'-l-lexamethylenedi(piperidinothio)-bis(phthalimide) When used with aconventional primary accelerator and sulfur, the compounds of structuralformula (I) provide a vulcanizable polymer with balanced processing andvulcanization characteristics. In many vulcanization systems theyprovide both improved scorch resistance and improved activationcharacteristics. In systems where they provide only improved scorchresistance or improved activation characteristics, they do so withoutadversely affecting the scorch resistance or conversely the activationcharacteristics. This is unique in that conventional retarders normallyadversely affect vulcanization rates, much less improve the rate; whileconventional activators normally adversely affect scorch, much lessimprove scorch resistance. Whether these compounds act as bothactivators and retarders, or just as an activator, or just as aretarder, is not only dependent upon the primary accelerator being usedbut also upon the particular polymer being vulcanized as well as theparticular sulfur donor compound of the present invention being used.The effect of accelerator systems, polymeric environment and differentsulfur donor compounds is illustrated herein lt should be noted,however, that regardless of the accelerator system used or theparticular polymer vulcanized, the compounds almost always act as sulfurdonors. In any case, the imides of the present invention will act atleast as one of the following; a sulfur donor, an activator or aretarder.

The amides of the present invention can be prepared by the reaction ofan aminesulfenyl chloride with an alkali metal salt of an amide.Alternatively, the aminesulfenyl chloride may be reacted with an imidein the presence of an organic acid acceptor such as pyridine ortriethylamine. The aminesulfenyl chlorides, in turn, may be preparedusing any of the available methods described in the literature, forexample, by chlorination of an N,N-dithiobis(amine), [German Patent965,968 (1954)], or by the reaction of a secondary amine with sulfurdichloride in the presence of an organic acid acceptor [German Patent1,131,222 (1962)]. Generally a solution of the aminesulfenyl chloride inan inert solvent is added to a solution or suspension of the imide (orits alkali metal salt), also in an inert solvent.

Alternatively, the imides can be prepared by reaction of animide-N-sulfenyl chloride with an appropriate amine in the presence ofan organic acid acceptor such as triethylamine or pyridine, or an excessof the amine which is entering into the reaction with the imide-N-sulfenyl chloride. The imide-Nsulfenyl chlorides, in turn, are readilyprepared as described in the literature by reaction of an imide withsulfur dichloride in the presence of an organic acid acceptor [U.S. Pat.No. 3,539,538 (1970)]. Generally, an amine is added to a solution of theimide-N-sulfenyl chloride in aninert solvent.

The performance of the compounds of the present invention as retarders,activators or in increasing the state of vulcanization is not dependentupon their method of preparation.

The imides of the present invention can be used with any conventionalcompounding additive such as carbon black, zinc oxide, antidegradantsand stearic acid. They can be used in a sulfurless system with anaccelerator (a sulfur donor or otherwise), preferably a primaryaccelerator, or with a sulfur vulcanization agent in the presence of anaccelerator. For the purposes of this invention, sulfur vulcanizingagent means elemental sulfur (free sulfur) or sulfur donatingvulcanizing agents, for example, an amine disulfide or a polymericpolysulfide. Preferably the imides are used with both a sulfurvulcanization agent, preferably free sulfur, and an accelerator,preferably a primary accelerator. The invention is applicable tovulcanization accelerators of various classes using conventionalaccelerator levels. Regardless of what accelerator is used, the imideswill still normally act as sulfur donors. For example, rubber mixescontaining the aromatic thiazole accelerators which includeN-cyclohexyl-2-benzothiazolesulfenamide, Z-mercaptobenzothiazole,N-tert-butyl-Z-benzothiazolesulfenamide, 2-benzothiazolyldiethyldithiocarbamate and 2-(morpholinothio)-benzothiazole can be used.Other thiazole accelerators which may be used include2-(aminodithio)-thiazoles and Z-(aminotrithio)-thiazoles such as2-(morpho1inodithio)-benzothiazole. Amine salts of mercaptobenzothiazoleaccelerators, for example, the t-butylamine salt ofmercaptobenzothiazole, and like salts of morpholine and 2,6-dimethylmorpholine can be used in the invention. Thiazole acceleratorsother than aromatic can be used. Stocks containing accelerators, forexample, tetramethylthiuram disulfide, tetramethylthiuram monosulfide,aldehyde amine condensation products, thiocarbamylsulfenamides,thioureas, xanthates, and guanidine derivatives are substantiallyimproved using the process of the present invention.

The imides of the invention can be used in any sulfur vulcanizablerubber including natural and synthetic rubbers and mixtures thereof.Synthetic rubbers that can be improved by the process of this inventioninclude homopolymers and copolymers of dienes, both conjugated andnonconjugated, e.g., 1,3-dienes such as 1,3-butadiene and isoprene.Examples of such synthetic rubbers include neoprene (polychloroprene),cis-l,4-polybutadiene, cis-l,4 polyisoprene, butyl rubber, copolymers of1,3-butadiene or isoprene with monomers such as styrene, acrylonitrileand methyl methacrylate. Ethylene/propylene terpolymers, for exampleethylenelpropylene/dicyclopentadiene terpolymers also benefit from thepractice of the present invention.

The imides can be added to the rubbers by any conventional techniquesuch as milling or Banburying.

All of the working examples herein are intended to illustrate but notlimit the scope of the present invention. Unless indicated otherwise,all parts are parts by weight.

The following examples, 1 to 7, illustrate the preparation of variousimides of the present invention, and are not intended to limit the scopeof the present invention.

EXAMPLE 1 To prepare N-(morpholinothio)-phthalimide, 0.50 mole ofchlorine gas was added during one-half hour to a mixture of 1 18.0 gramsof 4,4'-dithiobis(morpholine) in 500 ml. of toluene at 0-5 C. Theresulting solution of morpholinesulfenyl chloride was added during 1hour to a mixture of 147 grams (1.0 mole) phthalimide, 120 grams (1.2mole) triethylamine, and one liter tetrahydrofuran at 1015 C. After onehour, the mixture was poured into '1 .5 liters of water, the insolublesolid filtered, washed" on the filter with water, and recrystallizedfrom 2-propanolbenzene to afford 1613 grams (61.0%) of the producthaving a melting point of 210-212 0. Analysis of the product showed10.55 percent nitrogen and 12.13 percent sulfur. The percentagescalculated for C 1-1, N O S were 10.68 percent nitrogen and 12.12percent sulfur.

EXAMPLE 2 To prepare N-(diethylaminothio)-phthalimide, 0.20 mole ofchlorine gas was added during 15 minutes to a solution of 41.5 grams(0.20 mole) N,N'-dithiobis(diethylamine) in ml. of carbon tetrachlorideat 0-5 C. The resulting solution of diethylaminesulfenyl chloride wasadded dropwise to a mixture of 58.7 grams (0.40 mole) phthalimide, 48.5grams (0.48 mole) triethylamine, and 250 ml. of tetrahydrofuran at 010C. After one-half hour, the mixture was poured into three liters ofwater, extracted with chloroform, the combined extracts dried overanhydrous magnesium sulfate, and concentrated in vacuo. The resultingsolid residue was recrystallized twice from methanol, then stirred forten minutes in 350 ml. of ice cold one percent sodium hydroxide,filtered, washed on the filter with water and dried in vacuo. The yieldof product was 36.7 grams (36.7%) with a melting point of 7375 C.Analysis showed 11.06 percent nitrogen and 12.9 percent sulfur. Thepercentages calculated for C ll N O s were 11.20 percent nitrogen and12.8 percent sulfur.

EXAMPLE 3 To prepare N-(piperidinothio)-phthalimide, 0.20 mole ofchlorine gas was added to a solution of 46.4 grams (0.20 mole)N,N'-dithiobis(piperidine) in 100 ml. of carbon tetrachloride during 15minutes at 05 C. The resulting solution of piperidinesulfenyl chloridewas added dropwise during twenty minutes to a mixture of 58.7 grams(0.40 mole) phthalimide, 48.5 grams (0.48 mole) triethylamine, and 450ml. of tetrahydrofuran at 0-10 C. After one hour, the mixture was pouredinto 2.5 liters of water, sufficient chloroform added to dissolve theinsoluble solid, the lower layer drawn off, dried over anhydrousmagnesium sulfate, and concentrated in vacuo. The resulting solidresidue was recrystallized twice from 2-propanol-benzene, then stirredfor ten minutes in 550 ml. of ice cold 0.5 percent sodium hydroxide,filtered, washed on the filter with water and dried in vacuo. The yieldof product was 62.5 grams (59.6%) with a melting point of 177179 C.Analysis showed 10.57 percent nitrogen and 10.8 percent sulfur. Thepercentages calculated for C l-l N O s were 10.69 percent nitrogen and12.2 percent sulfur.

EXAMPLE 4 To prepare N-(diisopropylaminothio)-phthalimide, 0.25 mole ofchlorine gas was added to a solution of 67.1 grams (0.25 mole)N,N'-dithiobis(diisopropylamine) in 100 ml. of carbon tetrachlorideduring fifteen minutes at -5 C. The resulting solution ofdiisopropylaminesulfenyl chloride was added dropwise during one-halfhour to a stirred mixture of 74.5 grams (0.50 mole) phthalimide, 61.6grams (0.62 mole) triethylamine and 250 ml. of tetrahydrofuran at 0-10C. After one hour the mixture was poured into three liters of water,extracted with chloroform, the combined extracts dried over anhydrousmagnesium sulfate, and concentrated in vacuo. The oily solid residue wasslurried in hexane, filtered, then stirred in 650 ml. of ice cold 0.5percent sodium hydroxide for ten minutes, refiltered, washed with water,and recrystallized twice from methanol. The yield of product was 64.5grams (45.6%) with a melting point of 98100 C. Analysis showed 9.94percent nitrogen and 1 1.4 percent sulfur. The percentages calculatedfor C H N O S were 10.07 percent nitrogen and 11.5 percent sulfur.

EXAMPLE To prepare N-(morpholinothio)-cis-A -tetrahydrophthalimide, 0.10mole of chlorine gas was added to a solution of 23.6 grams (0.10 mole)4,4-dithiobis(morpholine) in 100 ml. of ethylene dichloride during tenminutes at-05 C. The resulting solution of morpholinesulfenyl chloridewas added dropwise to a mixture of 30.2 grams (0.20 mole)cis-N-tetrahydrophthalimide, 24.2 grams (0.24 mole) triethylamine, and250 ml. of ethylene dichloride. After one hour the reaction mixture wasfiltered, the filtrate concentrated in vacuo, the solid residue slurriedin heptane, refiltered, and recrystallized from 2-propanolbenzene. Theproduct was further purified by stirring for one-half hour in 200 ml. of25 percent potassium carbonate, filtering, washing with water, anddrying in vacuo. The yield of product was 27.0 grams (50.5%) with amelting point of l42-145 C. Analysis showed 10.47 percent nitrogen and11.83 percent sulfur. The percentages calculated for C H N O S were10.45 percent nitrogen and 1 1.94 percent sulfur.

The other compounds included within the practice of the presentinvention can be prepared by using the same or similar techniques asdescribed in the preceding working examples. Synthetic routes to thesecompounds are not limited, however, to these particular reactions andprocedures.

Tables 1, II, III and IV illustrate the use of various imides of thepresent invention with different rubber stocks. The compositions areintended only to be illustrative of the practice of the presentinvention and not limiting. Mooney Scorch tests were performed using thelarge rotor as described in ASTM D 1646-61. A recorder was employed tocontinuously plot viscosity Sulf versus time. The number of minutes(tAS) required for the viscosity curve to rise five points above theminimum was taken as a measure of scorch inhibition. Larger values for(M5) indicate a greater resistance to scorch or premature vulcanization.

Data on vulcanizing characteristics were obtained with a MonsantoOscillating Disc Rheometer, as described by Decker, Wise, and Guerry inRubber World, page 68, December 1962. Pertinent data from thisinstrument are: t the minutes required for the Rheometer torque curve torise four units above the minimum torque value, and the minutes requiredfor the torque curve to reach 90 percent of the difference between themaximum and minimum torque values.

The tgo value is considered to be the time required to reach the optimumvulcanized state. The difference, (r is indicative of the time necessaryfor actual vulcanization to take place after the scorch delay period hasended, i.e., is a relative measure of vulcanization rate. Compoundswhich increase 2 but do not greatly increase are preferred since theseimpart processing safety, yet do not require greatly extendedvulcanization times.

ARh is the difference between the maximum and minimum torque obtained onthe rheometer curve. It is used as a measure of the degree (state) ofvulcanization.

The following examples 6 to 26 illustrate the use of the sulfur donorsof the present invention in both natural rubber and SBR(butadiene/styrene elastomer). Stock A was used in examples 6 to 15while Stock B was used in examples 16 to 26. Both stocks were run withno imide (control), 0.5 part and 1.0 part of the imide.

Table 1 Stock A (parts) SBR 1712 Smoked sheets Carbon black 50 Stearicacid 3 Wax Zinc oxide Amine antioxidant ur 2-(Morpholinodithio)-benzothiazole lmide 0 The results obtained using Stock A are listed inTable [II and the results using Stock B in Table IV. The rheometer datawas obtained at a temperature of 275 F. in natural rubber and 302 F. inSBR. The Mooney Scorch data was determined at 250 F. in natural rubberand 270 F. in SBR.

The effect of the imides was measured by comparison with the control,i.e., the stock with no imide present. Ratios of the measurements forthe imide compounded stocks over the measurements for the control stockare listed in the tables. The c subscript indicates that the measurementwas made on the control stock. Values of ARh/ARh which are over 1.00indicate that the imidehas increased the state of vulcanization. Valuesof )/(t t which are less than 10, indicate an activating effect of theimide on the vulcanization rate. Values of tA /tA which are over 1.0indicate that the imide has increased the scorch delay time, i.e.,increased scorch resistance.

Table 11 contains a list of the various imides evaluated. 1

Table 11 lmide A N-(morpholinothio)-phthalimide BN-(diethylaminothio)-phthalimide C N-(pipendinothio)-phthalimide DN-(diisopropylaminothio)-phthalimide EN-(morpholinothio)-cis-A"-tetrahydrophthalimide FN-(N'-phenylcyclohexylaminothio)-phthalimide GN-(N'-B-cyanoethylcyclohexylaminothio)-phthalimide H N-(N-B-cyanoethyl-n-butylaminothio) phthalimide lN-(N'-ethylbenzylaminothio)- hthalimide .1 N-(N'-phenylbenzylaminothio-phthalimide K N-(N'-cyanomethylcyclohexylaminothio)-phthalimide Table111 Natural Rubber an- 4) ARh/ARh (t -u) tAS/tAS (parts) (parts) (parts)Exp. lmide 0.5 1.0 0.5 1.0 0.5 1.0

6 A 1.14 1.20 1.09 1.00 1.50 1.75 7 C 1.20 1.31 0.84 0.92 1.24 1.45 8 D1.13 1.19 0.91 0.84 0.90 0.87 9 E 1.14 1.23 0.85 0.87 1.32 1.45 10 F1.03 1.04 1.05 1.13 1.16 1.41 11 G 1.05 1.13 0.93 0.97 1.27 1.55 12, H1.11 1.18 0.87 0.93 1.42 1.65 13 l 1.15 1.21 0.85 0.88 1.36 1.50 14 J1.02 1.08 0.99 1.04 1.27, 1.47 15 K 1.12 1.19 1.02 1.04 1.27 1.47

Table IV SBR 90- 4) ARh/ARh, (t -t tAS/tAS (parts) (parts) (parts) Exp.lmide 0L5 1.0 0.5 1.0 0.5 1.0

16 A 1.09 1.20 0.78 0.74 1.26 1.42 17 B 1 1.14 1.24 0.65 0.53 0.92 -0.9718 C 1.09 1.15 0.63 0.51 0.90v 0.98 19 D 1.10 1.15 0.73 0.62 0.90 0.8720 E 1.05 1.13 0.87 0.76 1.05 1.18 21 F 0.99 0.98 0.94 0.90 1.12 1.20 22G 1.03 1.04 0.90 0.78 1.19 1.27 23 H 1.01 1.05 0.83 0.73 1.20 1.29 24. 10.98 1.07 0.79 0.63 1.12 1.22 25 .1 1.02 1.03 1.02 0.98 1.05. 1.18 26 K1.06 1.11 0.93 0.95 1.06 1.15

As shown in Table 111, all of the compounds acted as sulfur conors. Mostof the compounds acted as retarders. Also most acted as activators. Allof the compounds either performed as an activator or a retarder.

As shown in Table IV, all but two compounds acted as sulfur donors, andthese two acted as both activators and retarders. The three compoundswhich did not act as retarders, did act as activators, and the compoundwhich did not act as an activator, acted as a retarder.

N-(morpholinothio)-phthalimide was used incarbon black loaded naturalrubber (smoked sheet) with 2.5 parts of sulfur at both the 0.5 and 1.0part level, with 2-(morpholinodithio)-benzothiazole (0.5 part) in oneinstance and 0.5 part of 2-(2,6-dimethylmorpholinothio)-benzothiazole inanother. In the former case, the imide acted as a sulfur donor andretarder. In the latter instance, it acted as a sulfur donor, activatorand retarder. The imide was also used with 0.5 part of three otheraccelerators separately. When used with 2-(morpholinothio)-benzothiazoleand N-cyclohexyl-Z-benzothiazolesulfenamide, in both instances it actedas a 10 sulfur donor, a retarder and an activator. When used withN-t-butyl-2-benzothiazolesulfenamide, it acted as a sulfur donor and aretarder, while having only a small adverse effecton thevulcanizationrate.

N-(morpholinothio)-phthalimide was used in various other carbon blackloaded stocks containing free sulfur. In an NBR(butadiene/acrylonitrile) stock and a cis-l ,4 polyisoprene stock, itwas used with a primary/- secondary accelerator system and sulfur. Inboth cases the state of vulcanization and scorch delay period wereincreased. In a natural rubber/8BR cis-l,4 polybutadiene blend it wasused with a primary accelerator and sulfur and increased the state andrate of vulcanization and the scorch delay time. It was also used in anatural rubber composition containing sulfur and a primary acceleratorusing various activators (secondary accelerators). It provided anincreased rate and state of vulcanization. It was also used with freesulfur and a primary accelerator in a natural rubber/5BR blend and in acis-l,4 polybutadiene composition. In both cases the rate and state ofvulcanization were increased along with the scorch delay period. It wasalso used in natural rubber with both sulfur and a primary acceleratorusing diphenylguanidine in one case as a secondary accelerator andtetramethylthiuram disulfide in another instance. In both cases a higherstate of vulcanization and increased scorch delay timewere obtained.

The amide (0.5 part) was also used in a carbon black loaded smoked sheetcomposition, in one instance with benzothiazyl disulfide (0.5 part), andin another instance with 0.5 part of 2-mercaptobenzothiazole. In

both instances the imide increased the rate and state of vulcanizationand acted as a retarder.

The imide was also used in a smoked sheet natural rubber composition atboth the 0.5 and 1.0 part levels, in one instance with 1.0 part of2-(morpholinothio)- benzothiazole and in another instance withl.0 partof Z-mercaptobenzothiazole. In. every instance the imide.

acted to increase the state of vulcanization. Also, in every instance itincreased the rate of vulcanization with one exception (the sulfenamideat the 1.0 part level). With the sulfenamide it also acted as aretarder. It was also used at the 0.5 and 1.0 part levels with the2-(morpholinothio )-benzothiazole in combination with sulfur (2.75 part)and tetramethylthiuram disulfide. In both instances it increased thestate of vulcanization and the scorch delay time.

A natural rubber composition was cured without sulfur using 1, 1.5, and2.0 parts of the imide along with, in one instance, 0.5 partof2-(morpholinodithio) benzothiazole and in another instance with2-(morpholinothio)-benzothiazole. In each instance the state ofvulcanization and scorch delay period were increased.

The above examples are not intended to be limiting but ratherillustrative. Any of the sulfur donors, accelerators and rubbersdescribed earlier herein can be substituted in the preceding examples.In addition, the levels of the sulfur donors and other components insaid examples could be altered in accordance with the general teachingsherein.

The additives of this invention can be used at various concentrations aslow as 0.25 part per parts by weight of rubber and even as low as 0.10or even 0.05 part. Conventional levels would frequently be 0.5 and 1.0part, although levels as high as 1.5, 3.0, 5.0 and even 10 parts can beused. Most frequently the concentration ranges from 0.25 to 5.0 parts,more preferably 1 1 from 0.25 to 3.0 parts and most preferably from 0.251.50 parts. I

The sulfur donor compounds of the present invention are preferably addedto the rubbery polymer at the same time that the accelerator is added,although this order of addition is not necessary to the successfulutilization of the compounds of this invention.

The compounds of the present invention are effective in the presence oforganic accelerators whether they are diarylguanidines such asdiphenylguanidine, or thiazoles, more specifically benzothiazyl aminodisulfides, such as 2-(morpholinodithio)-benzothiazole, or thiazoles(also sulfenamides), more specifically thiazolesulfenamides, and evenmore specifically benzothiazolesulfenamides such as 2-(morpholinothio)benzothiazole and N-cyclohexyl-2-benzothiazolesulfenamide, i.e.,regardless of what type of organic accelerator is used. Thiuram sulfidessuch as tetramethylthiuram monosulfide and disulfide andtetraethylthiuram monosulfide and disulfide may also be used as well asother benzothiazolesulfenamides such as N-(t-butyl)-2-benzothiazolesulfenamide.

Various organic accelerators useful within the practice of thisinvention are described and illustrated in the Vanderbilt RubberHandbook, 1968 Edition, R. T. Van? derbilt Company, Inc., particularlyat pages 242 and 244 and also in the bulletin of the Elastomer ChemicalsDept. of the E. I. Du Pont de Nemours and Co. (inc) entitled,Accelerators, vulcanizing Agents and Retarders, Brochure No. SD AS4457.l I

The polymers in which the imides of the present invention areincorporated remain suitable for their art recognized .uses, e.g., intires and industrial products.

Compounds referred to earlier herein asbeing retarders and/or activatorsin natural rubber and SBR are merely illustrative and not limiting.

The balanced processing and vulcanization characteristics are most oftenobtained when free sulfur (ele mental sulfur) and a primary acceleratorare used with the imide.

Sometimes compounds are both a sulfur donor (and therefore a sulfurvulcanizing agent) and an accelera tor, e.g.,2-(morpholinodithio)-benzothiazole. Such compounds can be used with theimides, with or without another sulfur vulcanizing agent and/or anotheraccelerator.

The compounds of the present invention can be used effectively in anysulfur vulcanizable polymer and with any organic accelerating agent.

In addition to other preferred radicals mentioned earlier herein, apreferred form of R is the ethenylene radical.

Preferably when R is a saturated or olefinic divalent cyclic aliphaticradical, it contains 5 to 7 carbon atoms. When R is an arylene radical,preferably it contains 6 to 10 carbon atoms.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

I claim:

1; An imide having the following structural formula wherein R isselected from the group consisting of 4,5,-cyclohexenylene,orthophenylene, ethylene and l,3-propylene, and

is selected from the group consisting of morpholino,2,6-dimethylmorpholino, piperidino, diethylamino, diisopropylamino,3-methylpiperidino, t-butylamino, dicycloheiiylamino,N-B-cyanoethylcyclohexylamino, N-B-cyanoethyl-t-butylamino,N-B-cyanoethyl-nbutylamino, N-phenylcyclohexylamino, N- methylanilino,N-ethylanilino, N-ethylbenzylamino, dibenzylamino, N-phenylbenzylamino,N-cyanomethylcyclohexylamino and N-cyanomethyl-nbutylamino.

2. The imide according to claim 1 wherein the imide is selected from thegroup consisting of N-(morpholinothio)-phthalimide,N-(piperidinothio)-phthalimide andN-(morpholinothio)-cis-A-tetrahydrophthalimide.:

1. AN IMIDE HAVING THE FOLLOWING STRUCTURAL FORMULA
 2. The imideaccording to claim 1 wherein the imide is selected from the groupconsisting of N-(morpholinothio)-phthalimide,N-(piperidinothio)-phthalimide and N-(morpholinothio)-cis- Delta4-tetrahydrophthalimide.